I. Field of the Invention
The present invention relates generally to variable geometry turbine inlet nozzle assemblies and, more particularly, to such a nozzle assembly with cooling means.
II. Description of the Prior Art
In the conventional design of turbine engines, a turbine inlet nozzle assembly is provided within the gas stream passageway between the turbine engine combuster and the first turbine expander stage. The turbine inlet nozzle typically includes a plurality of circumferentially spaced vanes positioned within the gas stream passageway. In many of the previously known turbine engines, the nozzle vanes are fixed to the engine housing and, thus, are nonadjustable.
It is desirable, however, to variably adjust the throat area of the turbine inlet passageway for different power requirements of the turbine engine for maximum engine efficiency. One previously recognized method of variably restricting the throat area of the turbine inlet is to provide a turbine inlet nozzle with variable geometry, i.e., a turbine inlet nozzle in which the nozzle vanes are pivotally, rather than fixedly, mounted to the turbine engine housing. The previously known variable geometry inlet nozzle assemblies have also included some means to pivot or rotate the nozzle vanes in unison with each other.
The previously known variable geometry nozzle assemblies, however, have not proven entirely satisfactory for a number of different reasons. One disadvantage of the previously known variable geometry nozzle assemblies is that the means for pivoting the nozzle vanes have been incapable of pivoting all of the nozzle vanes in precise unison with each other. Such failure is due primarily to mechanical play in the actuating assembly. The inability to accurately pivot the nozzle vanes in unison with each other results in undesirable turbulences of the gas stream flow through the inlet nozzle and likewise degrades the overall efficiency of the turbine engine.
A still further disadvantage of the previously known variable geometry turbine inlet nozzles is that such nozzles are subjected to the high temperatures of the gas stream flow through the nozzle. As the temperature of the nozzle vanes become elevated, the vanes thermally distort the nozzle vane geometry and likewise degrade the overall efficiency of the turbine engine. Moreover, the vanes of the previously known variable geometry tubine nozzles have been rotatably mounted to the turbine support housing. Thus, thermal distortion of the support housing due to the high temperatures present within the nozzle gas stream also distort the geometry of the nozzle assembly.